This invention relates to equipment for use in marine operations and more particularly to the use of floating buoys in such operations.
Many different types of operations in a body of water, such as mineral exploration or salvage operations, make use of floating buoys which are utilized for various purposes, such as to indicate subsurface locations of interest or to secure lines of various types at the surface of the body of water to provide a convenient connection to undersea equipment. One particular application for such buoys, for example, involves the raising and lowering of anchors for non-powered vessels, such as barges. A discussion of this particular use for such buoys will serve to illustrate the design requirements and the problems which may be generally encountered in utilizing such floating buoys.
A barge is typically immobilized in a desired location by mooring lines leading from the vessel and connected to the shanks of one or more anchors embedded in the seabed. Such barges frequently are not equipped with their own hoisting means. Furthermore, it would be difficult to raise the anchor by raising the mooring line from the barge, since a force applied to the anchor line will tend to cause the anchor to dig in and hold even more firmly. Therefore, a second line, known as a pendant line, is commonly attached to the back portion, or "mud palm", of the anchor. When the pendant line is raised, the anchor will release without digging in. A second vessel, such as a tugboat which is equipped with a hoisting winch, is thus typically utilized to hoist each pendant line and thereby raise each barge anchor when the barge is to be relocated.
Floating buoys are frequently used to mark the surface locations above such anchors and to maintain the upper ends of the pendant lines at the surface so that a tugboat may readily locate and attach each pendant line to its hoisting equipment when the anchors are to be raised. The buoys which have been used for such an operation typically include a central core or hawse pipe through which the pendant line may freely travel. The upper end of the pendant line is terminated in an eye and the hawse pipe is provided with a stopper to prevent the eye from dropping through the hawse pipe. When the anchor is to be raised, the tugboat maneuvers sufficiently close to the location of the buoy and personnel on the boat retrieve the eye attached to the pendant line. The eye may then be connected to a hoisting winch on the tug and the pendant line reeled in, raising the attached anchor. During the hoisting operation, the pendant line slides through the hawse pipe of the buoy, and the buoy floats in the water adjacent to the side or stern of the boat, retained by the pendant line.
The necessarily close proximity between the buoy and the tugboat during such an operation can lead to problems. Such buoys are often large and somewhat massive structures, on the order of 10 feet in diameter. Particularly in rough or heavy seas, the buoy may strike the boat structure with considerable force, frequently causing damage to the boat or to the buoy or to both. In addition, the task of hooking the eye at the end of the pendant line can be very hazardous due to the erratic movements of the floating buoy which may occur relative to the tugboat, especially during rough or heavy seas.
In the past, a number of approaches have been attempted to resolve these problems. Many such buoys in the prior art were made of steel with pneumatic ballast tanks provided therein for flotation. The manufacturers of such buoys tended to make them heavier and stronger to avoid damage or destruction of the buoy in such operations, but heavier buoys tended to cause commensurately greater damage to the boat structure. Another approach which was tried involved providing spring steel bands around the buoy structure. The bands, however, were found to eventually develop jagged edges which caused further damage to a boat. Another attempted solution has involved redesigning the tug which is used to retrieve the buoy and raise the anchor. A catamaran type of tug has been developed, having twin hulls and a basket structure mounted between the hulls. The catamaran tug is maneuvered until the buoy is positioned within the tug between the hulls, and the basket is then used to catch the buoy and raise it out of the water, isolating it from wave motion. This approach helps to reduce the hazards involved in hooking the eye of the pendant line, but damage still may be caused to both the boat and the buoy structure by contact between them.
Other buoys have been developed which are manufactured from resilient materials and thus will yield upon contact and avoid damage to the boat structure. Such buoys typically have been made with a rubber or elastomeric outer skin filled with a foam material to provide flotation. These resilient buoy designs have helped to reduce or eliminate damage which otherwise was caused to the boat structure by contact with the buoy, but such buoys experience greatly reduced useful lifetimes due to the relative weakness of the resilient materials. It has been found that during such an anchor raising operation, the forces exerted on a resilient buoy by the pendant line and the inevitable contact with the boat tend to cause the resilient body of the buoy to be torn away from the central core or hawse pipe of the buoy. Such resilient buoys have been improved and strengthened by the addition of end caps which are made of a more durable material, such as steel. Such end caps, however, tend to some extent to reintroduce the problem of damage to the ship structure by contact with the buoy. Furthermore, even the stronger steel structure of the end caps may eventually be damaged in operation. Once such end caps are damaged, the resilient buoy can no longer be used.
Consequently, there has developed a need for a floating buoy whose construction will provide sufficient durability but which will not damage the structure of a ship when it is contacted by the buoy.
In addition, it would be advantageous to provide such a buoy which is repairable to thereby extend its useful life. In particular, it would be advantageous to provide such a buoy with components which are replaceable when worn or damaged.